I. Field of the Invention
The present invention relates generally to the area of surgical fixation, and more particularly to a surgical fixation system having an improved mechanism to prevent the back out of screws employed in securing a surgical fixation plate to an intended orthopedic location.
II. Discussion of the Prior Art
The use of surgical fixation systems involving plates is accepted practice for a variety of orthopedic procedures. One procedure experiencing proliferated growth is that of spinal fusion, wherein a surgical fixation plate is secured along two or more vertebral bodies through the use of screws extending through bores formed in the plate. Secured in this fashion, the surgical fixation plates serve to immobilize the vertebral bodies. When employed with bone allograft or another fusion-effecting implant (such as a mesh cage, a threaded cage, etc. . . . ), this immobilization promotes fusion to occur between the adjacent vertebral bodies, which is intended to restore disk height between the vertebral bodies and reduce pain in the patient.
A challenge exists in the use of spinal fixation plates, however, in that the screws employed to fix the spinal fixation plate to the vertebral bodies have a tendency to back out from the plate over time. One application where this is particularly worrisome is with the use of a spinal fixation plate positioned over the anterior cervical spine. More specifically, such backing out may cause the screws to come into unwanted contact with the esophagus, which may lead to damage or impairment to that organ. Another problem is that, with the screws backed out (partially or fully), the mechanical properties of the overall construct will become compromised, which may lead to a loss in the height of the intervertebral space height and thereby cause pain to the patient.
Various efforts have been undertaken to prevent the back out of screws employed in prior art surgical fixation plates. Some include a plurality of elements or components to engage the head of the screw within the through bore. Others provide one or more elements or components to cover the through bore after the screw has been introduced into the intended orthopedic location (e.g. a vertebral body). Unfortunately, both types of prior art systems have various drawbacks or imperfections. The first type (with a plurality of parts to engage the head of the screw within the through bore) can be challenging due to the plurality of parts and associated instrumentation, which may disadvantageously increase surgical time. The second type (covering the head of the screw) can similarly be time consuming and challenging based on the need for additional instrumentation to place the cover. Both types of systems may be more costly based on the need for additional instrumentation above and beyond the screwdriver instrument.
The present invention is directed at overcoming, or at least reducing the effects of, one or more of the problems set forth above.